Buku Teks
Stuart, Richard B.
Research Press Company, 1972
Buku Teks
Piaget, Jean, author
Routledge & Kegan Paul, 1975
Buku Teks
Ritzen, Jozef, author
Anthem Press, 2005
Buku Teks
Bianki, V., author
Foreign Languages Publishing, [date of publication not identified]
Buku Teks